Fermentation apparatus that uses biomass as feedstock

ABSTRACT

An apparatus for treating a biomass feedstock at a high temperature, includes a cooling device  90  for cooling a biomass treated liquid at a high temperature; an enzymatic saccharification tank  103  for saccharifying a cooled treated liquid  101 B with an enzyme; a solid-liquid separation apparatus  112  for removing water-slightly soluble substances contained in a saccharide solution  104  taken out from the enzymatic saccharification tank  103  and a foreign substance removing unit  113  provided with a microfiltration (MF) membrane  113   a ; a dilution tank  132 , disposed downstream of the foreign substance removing unit  113 , for diluting the saccharide solution from which the water-slightly soluble substances are removed by adding water thereto; a water separation unit  116 , provided with a reverse osmosis (RO) membrane  116   a , for removing water  114  from the diluted saccharide solution so as to obtain concentrated saccharide solution  115.

FIELD

The present invention relates to a fermentation apparatus that usesbiomass as a feedstock.

BACKGROUND

Production technology of ethanol or the like has hitherto beenpractically used in which after saccharification treatment of biomasssuch as wood with dilute sulfuric acid or concentrated sulfuric acid,solid-liquid separation is performed, and an aqueous phase isneutralized, which is utilized as a feedstock for ethanol fermentation(Patent Literature 1, and Patent Literature 2).

Chemical industry feedstock production (for example, lactic acidfermentation, and the like) using saccharide as a starting feedstock canalso be considered.

Here, biomass refers to an accumulation of organisms or organicsubstances derived from an organism, which is incorporated in a materialcycle in the global biosphere (see JIS K 3600 1258).

Here, sugarcanes, corns, and the like, which are now used as thefeedstock for an alcohol, are originally provided for food, and thus itis not preferable that these edible resources are stably employed forindustry for long term in terms of the life cycle of availablefoodstuffs.

Thus, effective utilization of cellulose resources such as herbaceousbiomass or woody biomass, which are expected to be useful resources inthe future, is an important issue.

In addition, the cellulose resource include variously such as 38 to 50%cellulose, a 23 to 32% hemicellulose component, and a 15 to 22% lignincomponent, which is not a fermentation feedstock, which are eachdifferent. Because of industrialization research with many problems,only fixed feedstock is considered, and production system technologyconsidering versatility of feedstock has not yet been disclosed in thepresent circumstances.

In addition, the production system in which the fixed feedstock isconsidered has little point, because it is, originally, considered forthe purpose of measurements of garbage problem or prevention of globalwarming in a manner disadvantageous to the fermentation feedstock,compared to a starch feedstock. General waste must be widely applicable.Enzymatic saccharification method itself has also excessive lowefficiency, which is a prospective issue in the present circumstances. Asaccharification ratio with an acid treatment is considerably smallvalue such as about 75% (based on a component capable ofsaccharification), because of overdecomposition of saccharide caused byan excessive reaction. A production ratio of ethanol is, accordingly, upto about 25% to a cellulose resource (Non Patent Literature 1 and PatentLiterature 3).

Additionally, according to the conventional techniques of PatentLiteratures 1 to 3, by-products cause enzymatic saccharificationinhibition, thereby occurring a phenomenon in which a saccharide yieldis reduced, and thus hydrothermal decomposition apparatuses, by whichenzymatic inhibitory substances are removed to increase saccharificationactivity of enzyme by mainly cellulose, have been previously proposed(Patent Literatures 4 and 5).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese National Publication of International    Patent Application No. 9-507386-   Patent Literature 2: Japanese National Publication of International    Patent Application No. 11-506934-   Patent Literature 3: Japanese Laid-open Patent Publication No.    2005-168335-   Patent Literature 4: Japanese Laid-open Patent Publication No.    2009-183805-   Patent Literature 5: Japanese Laid-open Patent Publication No.    2009-183154

Non Patent Literature

-   Non Patent Literature 1: Nikkei Biotechnology Business, p 52,    September 2002

SUMMARY Technical Problem

According to the proposal of the hydrothermal decomposition apparatus inPatent Literatures 4 and 5 described above, biomass and pressurized hotwater are supplied while they are brought into countercurrent contact toeach other, to perform hydrothermal reaction due to internal heatexchange, but the internal temperature is a high temperature of 180 to240° C., and a pressure 0.1 to 0.4 MPa higher than the saturated vaporpressure of water at that temperature is applied to perform thedecomposition treatment, thus resulting in containing with decompositionproducts of lignin and the like in the biomass treated liquid at a hightemperature (pressurized hot water effluent) after the reaction.

It has been revealed that with respect to a pressurized hot watersoluble component dissolved in this biomass treated liquid at a hightemperature, a part of the pressurized hot water soluble component,which has been once dissolved in pressurized hot water, is precipitated,and is solidified or is formed into a colloidal water-slightly solublesubstance, because the reaction mixture is cooled to an enzymaticsaccharification temperature (for example, 60° C. or lower), in asaccharification step of a subsequent step. It has been further found inthe present invention that this water-slightly soluble substance has aninhibitory function of growth of microorganisms and fermentationproduction in the fermentation step of the subsequent step.

Thus, the present invention provides a fermentation apparatus that usesbiomass as a feedstock, which includes an apparatus capable ofefficiently removing water-slightly soluble substances, which aregenerated during decomposition of a biomass feedstock in conditions of ahigh temperature and a high pressure, after enzymatic saccharification,which are the problems described above.

Solution to Problem

According to a first aspect of the present invention, there is provideda fermentation apparatus that uses biomass as a feedstock including: ahydrothermal decomposition apparatus for performing a high temperatureand high pressure treatment in a temperature range of 180° C. to 240°C., while bringing a biomass feedstock including at least cellulose,hemicellulose, and lignin into countercurrent contact with pressurizedhot water; a cooling means for cooling biomass treated liquid at a hightemperature which has been discharged from the apparatus; an enzymaticsaccharification tank for saccharifying the cooled treated liquid withan enzyme; a solid-liquid separation apparatus for removing awater-slightly soluble fermentation inhibitory substance contained inthe saccharide solution taken from the enzymatic saccharification tank;a foreign substance removing unit provided with a microfiltration (MF)membrane; a dilution tank disposed downstream of the foreign substanceremoving unit for adding water so as to dilute the saccharide solutionfrom which the water-slightly soluble fermentation inhibitory substancehas been removed; a water separation unit provided with a reverseosmosis (RO) membrane, for removing water from the diluted saccharidesolution so as to obtain concentrated saccharide solution; and afermentation tank for fermenting the concentrated saccharide solution.

According to a second aspect of the present invention, there is providedthe apparatus according to the first aspect, including: a saccharidesolution purification tank for retaining the saccharide solution takenout from the enzymatic saccharification tank; a solid-liquid separationunit disposed via a first circulation line from the saccharide solutionpurification tank, for removing a water-slightly soluble fermentationinhibitory substance from the taken saccharide solution; and a foreignsubstance removing unit disposed via a second circulation line from thesaccharide solution purification tank, the foreign substance removingunit including a microfiltration (MF) membrane for removing awater-slightly soluble fermentation inhibitory substance from the takensaccharide solution.

According to a third aspect of the present invention, there is providedthe apparatus according to the second aspect, in which the enzymaticsaccharification tank and the saccharide solution purification tank areintegrated.

According to a fourth aspect of the present invention, there is providedthe apparatus according to the third aspect, including a dilution tankfor adding water so as to dilute the saccharide solution which has beentreated in the foreign substance removing unit to remove thewater-slightly soluble substance therefrom; and a water separation unitincluding a reverse osmosis (RO) membrane for separating water from thediluted saccharide solution.

According to a fifth aspect of the present invention, there is providedthe apparatus according to any one of the first to fourth aspects,including a first measurement unit for measuring either or both of aturbidity or/and an absorbance of the saccharide solution from which thewater-slightly soluble fermentation inhibitory substance has beenremoved.

According to a sixth aspect of the present invention, there is providedthe apparatus according to the fifth aspect, including a secondmeasurement unit for measuring either or both of a turbidity and anabsorbance of the saccharide solution after addition of yeast.

Advantageous Effects of Invention

According to the apparatus of the present invention, water-slightlysoluble fermentation inhibitory substances, which are generated during ahigh temperature and high pressure treatment at 180° C. to 240° C. whilea biomass feedstock including at least cellulose, hemicellulose andlignin is brought into countercurrent contact with pressurized hotwater, is completely removed, whereby saccharide solution having lessimpurities can be obtained. As a result, it is also possible toconcentrate the saccharide solution using reverse osmosis membrane in asubsequent stage, whereby the saccharide solution having a higherconcentration than those in conventional methods can be produced.Fermentation inhibition can be suppressed with the improvement of thesaccharide solution described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a fermentation apparatus that uses biomassas a feedstock according to Example 1.

FIG. 2 is a schematic view of a fermentation apparatus that uses biomassas a feedstock according to Example 2.

FIG. 3 is a schematic view of a fermentation apparatus that uses biomassas a feedstock according to Example 3.

FIG. 4 is a measured chart of a high-performance liquid chromatography.

FIG. 5 is a view illustrating results of decreased amounts of carbondioxide in an ethanol fermentation test.

FIG. 6 is a view illustrating results of decreased amount of carbondioxide in an ethanol fermentation test.

FIG. 7 is a schematic view illustrating a hydrothermal decompositionapparatus of biomass according to Example 1.

DESCRIPTION OF EMBODIMENTS

The present invention will be explained in detail in reference to viewsbelow. The present invention is not limited to these Examples. Inaddition, constituent features described in Examples below include onewhich can be easily considered by those skilled in the art and oneswhich are substantially the same as those.

Example 1

The fermentation apparatus using a biomass feedstock according to thepresent invention will be explained in reference to views.

FIG. 7 is the schematic view illustrating a hydrothermal decompositionapparatus of biomass according to Example 1.

First, a “hydrothermal decomposition apparatus (50) in which a hightemperature and high pressure treatment is performed at a temperaturerange of 180° C. to 240° C. while a biomass feedstock including at leastcellulose, hemicellulose and lignin is brought into countercurrentcontact with pressurized hot water” is explained using FIG. 7.

The hydrothermal decomposition apparatus 50 is a vertical typeapparatus, as illustrated in FIG. 7, but the present invention is notlimited thereto, and may be an inclined type or horizontal-typehydrothermal decomposition apparatus. As the hydrothermal decompositionapparatus, the inclined type and the vertical type are more preferable.This is because gases generated during hydrothermal decompositionreaction and gases carried in a feedstock can quickly escape from upperparts, which is preferable. In addition, because decomposition productsare extracted with pressurized hot water 55, a concentration of extractsis increased from an upper side toward a bottom side, which is thuspreferable in terms of extraction efficiency.

According to the hydrothermal decomposition apparatus 50 of the presentExample, a conveying screw means 54 is provided; as a result, 1) a solidcomponent can be conveyed by solid-liquid counter-flow, 2) solid-liquidseparation can be performed in an apparatus body 53, and 3) mixing ofpressurized hot water 55 on the surface and the inside of the solid isadvanced in the apparatus body 53, whereby the reaction is promoted.

In the hydrothermal decomposition apparatus 50 according to the presentExample, a biomass feedstock (for example, a straw, and the like in thepresent Example) 51 is supplied through a biomass supplying apparatus 52at a normal pressure or under pressure; pressurized hot water 55 issupplied from an edge side different from the supplying side of thebiomass feedstock 51 into the inside of the apparatus body 53;hydrothermal decomposition is performed while the biomass feedstock 11is brought into countercurrent contact with the pressurized hot water 55to transfer a lignin component and a hemicellulose into the pressurizedhot water 55, thereby separating the lignin component and thehemicellulose component from the biomass feedstock 51; and a biomasssolid component 56 is discharged through a biomass discharging apparatus57 under pressure or at a normal pressure. In the view, reference sign58 shows pressurized nitrogen.

Here, the biomass feedstock, which is supplied to the hydrothermaldecomposition apparatus 50, is not particularly limited, and refers toan accumulation of organisms or organic substances derived from anorganism incorporated in a material cycle in the global biosphere (seeJIS K 3600 1258). In the present invention, it is particularlypreferable to use cellulose resources such as wood including, forexample hardwoods, and herbaceous plants, agricultural wastes, foodwastes.

The particle size of the biomass feedstock is not particularly limited,and it is preferable to mill it to a size of, for example, five mm orless.

In the present Example, a pre-treatment using a mill as a pre-treatmentapparatus may be performed before the biomass is supplied. Washing usinga washing apparatus may also be performed.

When as the biomass feedstock was used for, for example, chaff, it canbe supplied to the hydrothermal decomposition apparatus 50 as it is,without the mill treatment.

It is preferable to set a reaction temperature in the hydrothermaldecomposition apparatus 50 at a range of 180° C. to 240° C., morepreferably 200° C. to 230° C.

This is because a hydrothermal decomposition speed is slow at a lowtemperature of lower than 180° C., and thus a long retention time isrequired, leading to increasing in size of the apparatus, which is notpreferable. On the other hand, when the temperature is higher than 240°C., the decomposition speed becomes excessive, which increases thetransfer of the cellulose component from the solid to the liquid sideand, at the same time, promotes the excessive decomposition of thehemicellulose saccharides, which is not preferable.

The hemicellulose component starts to dissolve at about 140° C., thecellulose starts to dissolve at about 230° C., and the lignin componentstarts at about 140° C. It is preferable to set a temperature to a rangeof 180° C. to 240° C., where the cellulose remains on the solidcomponent side, and the hemicellulose component and the lignin componenthave sufficient decomposition speeds.

It is preferable to set a reaction pressure to a pressure about 0.1 to0.5 MPa higher than a saturated vapor pressure of water having eachtemperature at which the pressurized hot water 55 exists inside theapparatus body 53.

The reaction time is preferably 20 minutes or less, or from threeminutes to 10 minutes. This is because if the reaction is continued fora long time, a ratio of the excessively decomposed products isincreased, which is not preferable.

In the hydrothermal decomposition apparatus 50, when the biomassfeedstock 51 is brought into countercurrent contact with the pressurizedhot water 55, it is preferable to make uniform pressurized hot waterflow.

Biomass treated liquid at a high temperature 101A in the presentinvention can be obtained by using such a hydrothermal decompositionapparatus 50.

The pressurized hot water 55 may have any pH value of alkaline, neutraland acidic ranges. When it is alkaline, sodium hydroxide, hydrated lime,ammonia, and the like may be used, and when it is acidic, dilutesulfuric acid, hydrochloric acid, phosphoric acid, and the like may beused. When the pressurized hot water 55 is alkaline or acidic, it has anadvantage in which the pre-treatment of the biomass can be efficientlyadvanced. On the other hand, however, it has disadvantages in which itis necessary to complete the pH adjustment before enzyme is thrown, andit is necessary to prepare chemicals for adjusting the pH and to providea pH adjusting apparatus.

FIG. 1 is the schematic view of the fermentation apparatus that usesbiomass as a feedstock according to Example 1.

Next, a fermentation apparatus 200A that uses biomass as a feedstockwill be explained using FIG. 1, which includes cooling means 90 in whichthe biomass treated liquid at a high temperature 101A, which has beendischarged from the hydrothermal decomposition apparatus 50 in FIG. 7,is cooled; an enzymatic saccharification tank 103 in which a cooledtreated liquid 101B is subject to saccharification with an enzyme; asolid-liquid separation apparatus 112 in which the water-slightlysoluble fermentation inhibitory substances contained in saccharidesolution 104, which has been taken out from the enzymaticsaccharification tank 103, are removed and a foreign substance removingunit 113 provided with a microfiltration (MF) membrane 113 a; a dilutiontank 132 which is disposed downstream of the foreign substance removingunit 113 and in which the saccharide solution 104 from which thewater-slightly soluble fermentation inhibitory substances has beenremoved is diluted by adding water thereto; a water separation unit 116provided with a reverse osmosis (RO) membrane 116 a capable of removingwater 114 from the diluted saccharide solution 104 to obtainconcentrated saccharide solution 115; and a fermentation tank 141 inwhich the concentrated saccharide solution 115 is subjected tofermentation.

Yeast 142 is added to the fermentation tank 141, thereby obtainingfermentation liquid 143. The fermentation liquid 143 is separatelysubjected to distillation treatment to obtain a desired fermentationproduct.

According to the present Example, a solid-liquid separation apparatus112 is disposed as an apparatus for removing the water-slightly solublefermentation inhibitory substances which are contained in the saccharidesolution 104 taken out from the enzymatic saccharification tank 103, anda foreign substance removing unit 113 provided with a microfiltlationmicrofiltration (MF) membrane 113 a is further disposed downstreamthereof.

When the apparatus for removing the water-slightly soluble fermentationinhibitory substance is disposed, the water-slightly solublefermentation inhibitory substances are removed from the biomass treatedliquid at a high temperature generated by decomposing the biomassfeedstock in conditions of a high temperature and a high pressure,whereby the saccharide solution including less impurities can beobtained, thus resulting in performance of good fermentation.

Here, it has been confirmed by the present inventors that thewater-slightly soluble fermentation inhibitory substances in the presentinvention are substances different from furfural and HMF(5-hydroxymethyl furfural), which are generally known as fermentationinhibitory substances, though further details about such substances havenot been unraveled yet, as explained in Experiment Examples describedbelow.

For example, according to a known hydrothermal decomposition treatment,the biomass and the pressurized hot water are supplied so that they arebrought into countercurrent contact with each other, thereby performingthe hydrothermal reaction due to the internal heat exchange, asdescribed above. At that time, the reaction condition is that atemperature is high such that the internal temperature is from 180° C.to 240° C. and, at the same time, a pressure 0.1 to 0.4 MPa higher thanthe saturated steam pressure of water having a temperature at that timeis applied, and thus reaction decomposition products of lignin and thelike are included in the biomass treated liquid at a high temperature(pressurized hot water effluent) after the reaction.

The pressurized hot water soluble component dissolved in this biomasstreated liquid at a high temperature is cooled to an enzymaticsaccharification temperature (for example, 60° C. or lower), in asaccharification step of a subsequent step, and thus a part of thepressurized hot water soluble component, which has been once dissolvedin pressurized hot water, is precipitated, and is solidified or isformed into a colloidal water-slightly soluble substance.

When the biomass feedstock is subjected to a decomposition treatment atan ordinary temperature, accordingly, these water-slightly solublesubstances do not exist on the liquid side, and thus it can be assumedthat the water-slightly soluble substances are unique substances in thebiomass treated liquid at a high temperature.

According to the present invention, such water-slightly solublefermentation inhibitory substances are removed by means of a saccharidesolution purification means 110, whereby the purification is performedin the saccharification treatment, and thus in a subsequent fermentationstep it is possible to perform good fermentation treatment and toimprove a fermentation efficiency in an alcohol fermentation, asexplained in Experiment Examples described above.

Here, the saccharide solution purification means 110 includes, asillustrated in FIG. 1, the solid-liquid separation apparatus 112 inwhich solid residue 111 such as lignin including the water-slightlysoluble fermentation inhibitory substances 111 is separated from thesaccharide solution 104 taken out from the enzymatic saccharificationtank 103, and the foreign substance removing unit 113 provided with themicrofiltlation (MF) membrane 113 a in which the remainingwater-slightly soluble fermentation inhibitory substance is furtherremoved from the saccharide solution 104, which has been separated inthe solid-liquid separation apparatus 112.

As the solid-liquid separation apparatus 112, for example, a screwdecanter, a sand separator, an MF membrane, and the like may be used.The solid substances are removed by using this to protect the ROmembrane 116 a.

The alcohol fermentation apparatus 200A that uses biomass as a feedstockaccording to the present Example include the dilution tank 132 in whichwater (RO water) 131 was added to the saccharide solution 104 from whichthe water-slightly soluble fermentation inhibitory substances have beenremoved to dilute it. In FIG. 1, reference sign P₆ shows a liquidsending pump for sending dilution water 133 to the water separation unit116.

When addition of water before the solid substances are removed, only thewater-slightly soluble fermentation inhibitory substance in an amount ofits solubility is dissolved, and thus a concentration of thefermentation inhibitory substance is not reduced. When the dilution withwater is performed after the water-slightly soluble fermentationinhibitory substances are removed, however, it is possible to removeorganic acids (for example, acetic acid) and the like other than thedecomposition products such as lignin, and to perform the fermentationwith high efficiency in the subsequent steps.

Water 114 was removed from the dilution water 133, which has beendiluted in the dilution tank 132, through the water separation unit 116having the RO (Reverse Osmosis: RO) membrane 116 a to concentrate it toa pre-determined concentration, thereby obtaining concentratedsaccharide solution 115.

Subsequently, the concentrated saccharide solution 115 is sent to thefermentation tank 141, to which yeast 142 is added to obtain thefermentation liquid 143.

In the water separation unit 116, a loose RO membrane, a nanofiltrationmembrane (NF membrane), and the like may be used.

In the present Example, in order to remove the solid residue 111 such aslignin including the water-slightly soluble fermentation inhibitorysubstance, the solid-liquid separation treatment in the solid-liquidseparation apparatus 112 and the membrane treatment in the foreignsubstance removing unit 113 are preformed, whereby the fermentationinhibitory substances can be effectively removed.

In particular, many zymocytes capable of fermenting saccharide solution(C5 saccharide), which is obtained by subjecting the hemicellulose,which is the pressurized hot water soluble component, to thesaccharification, have poor ethanol resistance and poor resistance tofermentation inhibitory substances, and thus it is important to fit tothe resistances of the zymocyte. The present invention can realize it.In fermentation in which a recombinant yeast cannot be used, theresistance of the zymocyte remarkably becomes problems, but the problemscan be solved by the present invention.

The decomposition products of the water-slightly soluble fermentationinhibitory substance including lignin are removed during the treatmentof the saccharide solution 104, and thus the precipitation of theforeign substances on the RO membrane 116 a, which is disposeddownstream and is used for separating water, can be prevented, wherebythe membrane life of the RO membrane 116 a can be prolonged.

Next, the treatment procedure of the alcohol fermentation apparatus 200Ausing this biomass will be explained.

As the pressurized hot water effluent in the present invention mainlyincludes the hemicellulose component, the saccharide solution ispurified when C5 saccharide and membrane treatment is performed, inwhich this pressurized hot water soluble component is subjected toenzymatic saccharification to form pentose (C5 saccharide).

<Enzymatic Saccharification Step>

First, the biomass treated liquid at a high temperature (pressurized hotwater effluent) 101A is introduced into the enzymatic saccharificationtank 103, to which enzyme 102 is added, and the saccharification isperformed by the enzyme reaction in the enzymatic saccharification step.

<Solid-Liquid Separation Step>

Next, the saccharide solution 104 is retained in a first saccharidesolution tank 121. After that, the solid residue 111 such as ligninincluding the water-slightly soluble fermentation inhibitory substancesis separated through the solid-liquid separation apparatus 112, and thenthe saccharide solution 104 is retained in a second saccharide solutiontank 122.

<Foreign Substance Removing Step>

Next, remaining foreign substances, such as solid residue 111 such aslignin including the water-slightly soluble fermentation inhibitorysubstances, are membrane-separated from the saccharide solution 104through the foreign substance removing unit 113 provided with the MFmembrane 113 a, and then the saccharide solution 104 is retained in thedilution tank 132.

The saccharide solution 104 including the foreign substances, which havenot been removed, is returned to the first saccharide solution tank 121or the second saccharide solution tank 122.

<Saccharide solution Dilution Step>

Next, water (RO water) 131 is added to the saccharide solution 104, fromwhich the water-slightly soluble fermentation inhibitory substances havebeen removed, in the dilution tank 132 to obtain the dilution water 133.

<Saccharide Concentration Step>

Next, water 114 is removed from the dilution water 133 through the waterseparation unit 116 provided with the RO membrane 116 a to obtain theconcentrated saccharide solution 115.

A first measuring unit of measuring either or both of a turbidity and anabsorbance of the concentrated saccharide solution 115, which has beenpurified through the saccharide solution purification means 110 and fromwhich the water-slightly soluble substances have been removed, (forexample, a turbidimeter and/or a absorption spectrometer) may beincluded.

In order to monitor a degree of the impurity removal in the concentratedsaccharide solution 115 (a degree of clarity of the saccharide solution104), the turbidity and/or the absorbance are/is measured in the firstmeasurement unit.

As a result, it is possible to confirm the sufficient removal of thewater-slightly soluble substances from the concentrated saccharidesolution 115, whereby the quality of the saccharide solution 104 can becontrolled by the turbidimeter and/or the absorption spectrometer basedon the degree of clarity.

In addition, because it is comprehended that the saccharide solution 104is sufficiently clear in the first measurement unit, the process controlof the ethanol production in the fermentation step can be performed inthe second measurement unit by change in the degree of clarity, i.e. theincrease or decrease of the degree of clarity, caused by proliferationof yeast 142 in the subsequent step.

<Fermentation Step>

Next, the concentrated saccharide solution is purified in the saccharidesolution purification means 110, and is introduced into a fermentationtank 141, and yeast 142 is added thereto, whereby, for example, alcoholfermentation in the fermentation step is performed.

In FIG. 1, reference signs M₁ to M₃ show motors which drive the stirringmeans in the enzymatic saccharification tank 103 and the first andsecond saccharide solution tanks 121 and 122, M₅ shows a motor whichdrives the stirring means by which the stirring is performed in thefermentation tank 141, P₁ to P₃ show liquid sending pumps for sendingthe saccharide solution 104, and P₅ shows a liquid sending pump forsending the ethanol fermentation liquid 143.

As described above, according to the present Example, the saccharidesolution having less impurities can be obtained by removing thewater-slightly soluble fermentation inhibitory substances, which areincluded in the biomass treated liquid at a high temperature 101Agenerated by decomposition of the biomass feedstock in conditions of ahigh temperature and a high pressure through the saccharide solutionpurification means 110, and the fermentation inhibition can besuppressed in the fermentation treatment in the subsequent alcoholfermentation step, thus resulting in performance of good fermentation.

Example 2

Next, a fermentation apparatus that uses biomass as a feedstock will beexplained in reference to a view.

FIG. 2 is the schematic view of the fermentation apparatus that usesbiomass as a feedstock according to Example 2. The same reference signsare applied to the same members as those in the apparatus of Example 1,and the explanations thereof are omitted.

As illustrated in FIG. 2, a saccharide solution purification means 110having a structure different from that in Example 1 illustrated in FIG.1 is disposed in a fermentation apparatus 200B that uses biomass as afeedstock.

The saccharide solution purification means 110 illustrated in FIG. 2includes a saccharide solution purification tank 151 in which saccharidesolution 104 taken out from an enzymatic saccharification tank 103 isretained; a solid-liquid separation apparatus (for example,centrifugation) 112 which is disposed via a first circulation line L₁from the saccharide solution purification tank 151, and in whichwater-slightly soluble fermentation inhibitory substances (solid residue111 such as lignin) is removed from the taken saccharide solution 104;and a foreign substance removing unit 113 which is disposed via a secondcirculation line L₂ from the saccharide solution purification tank 151,and which includes a microfiltration (MF) membrane 113 a removingwater-slightly soluble fermentation inhibitory substances from the takensaccharide solution 104.

In FIG. 2, reference sign M₆ shows a motor which drives a stirring meansin the saccharide solution purification tank 151.

According to the saccharide solution purification means 110 of Example1, the membrane treatment is sequentially performed, but according tothe saccharide solution purification means 110 of Example 2 thesaccharide solution purification tank 151 has two circulation lines (thefirst circulation line L₁ and the second circulation line L₂), and thusthe treatment appropriate to the concentration condition of thewater-slightly soluble fermentation inhibitory substance (solid residue111 such as lignin) can be performed.

When a content of the water-slightly soluble fermentation inhibitorysubstance (solid residue such as lignin) is higher than a pre-determinedvalue, accordingly, the treatment using both of the first circulationline L₁ and the second circulation line L₂ is performed to remove thewater-slightly soluble fermentation inhibitory substances.

When the content of the water-slightly soluble fermentation inhibitorysubstance is low, the membrane treatment using the second circulationline L₂ alone can be performed. If necessary, the solid-liquidseparation treatment may be performed.

Example 3

Next, the fermentation apparatus that uses biomass as a feedstockaccording to the present invention will be explained in reference to aview.

FIG. 3 is a schematic view of a fermentation apparatus that uses biomassas a feedstock according to Example 3. The same reference signs areapplied to the same members as those in the apparatuses of Examples 1and 2, and the explanations thereof are omitted.

As illustrated in FIG. 3, an alcohol fermentation apparatus 200C thatuses biomass as a feedstock includes a saccharide solution purificationtank 161 in which the enzymatic saccharification tank 103 in thesaccharide solution purification means 110 of Example 2 and thesaccharide solution purification tank 151 are integrated.

In the view, reference sign M₇ shows a motor which drives a stirringmeans in the saccharide solution purification tank 161.

According to Example 2, the enzymatic saccharification tank 103 and thesaccharide solution purification tank 151 are separately disposed, butaccording to the present Example, installation space-saving can becontemplated by integrating them.

Experiment Example 1

<Identification Test of Water-Slightly Soluble Fermentation InhibitorySubstance>

Cooled biomass treated liquid at a high temperature and each of varioussolvents were mixed in a ratio of 1:9, and the identification wasperformed using a high-performance liquid chromatography apparatus.

The biomass treated liquid at a high temperature was obtained byhydrothermally decomposing rice straw in a pressurized condition havinga temperature of 180° C. using a hydrothermal decomposition apparatus 50illustrated in FIG. 7, and a pressurized hot water effluent 101A wasused.

Acetonitrile, acetone, and methanol, which are all polar solvents, wereused as a solvent. Pure water, which had been filtered through “MILLI-Q”(trademark), was used as Comparative Example.

The procedures are as follows: the cooled biomass treated liquid at ahigh temperature was mixed with these solvents and water, and themixtures were allowed to stand in a refrigerator (4° C.) over night.

After that, centrifugal separation (15,000 rpm, 10 minutes, 4° C.) wasperformed, and supernatant liquid was recovered and the liquid wastreated with a filter (0.45 μm).

This test liquid (Test 1-1: acetonitrile, Test 1-2: acetone, Test 1-3:methanol, and Test 1-4: pure water), after treated with the filter wasanalyzed using high-performance liquid chromatography (HPLC).

ODS column (SYNERGI: 4μ, Hydro-RP80A 4.6×250 mm, manufactured byPhenomenex Company) was used as the column.

Water-acetonitrile solvent was used as eluent, which was subjected to agradient treatment of an acetonitrile concentration of 8% to 100%.

A detection wavelength was set at 220 nm.

The results are shown in FIG. 4 and Table 1.

TABLE 1 Unknown peak (RT: 22.6 min, Furfural Acetonitrile 55%) (1-1)Acetonitrile 2469009 160550 (1-2) Acetone 2513992 157743 (1-3) Methanol2428062 145366 (1-4) Pure water 2433687 22275

FIG. 4 illustrates a measured chart of high-performance liquidchromatography.

As shown in FIG. 4 and Table 1, HMF (5-hydroxymethyl furfural: anelution time of around 6.5 minutes) and furfural (an elution time ofaround 10.5 minutes), which are known fermentation inhibitorysubstances, were detected in All of Tests 1-1 to 1-4.

On the other hand, an unknown component was identified at an elutiontime of around 22.6 minutes in Tests 1-1 to 1-3. In Test 1-4, theunknown peak component was not detected.

From the above, it was proved that the biomass treated liquid at a hightemperature was contained with a water-slightly soluble substance.

Experiment Example 2

<Fermentation Test According to Presence or Absence of Water-SlightlySoluble Fermentation Inhibitory Substance>

Fermentation of the saccharification liquid using the cooled biomasstreated liquid at a high temperature was performed, and CO₂ decreasedamounts in the fermentation were compared.

Pichia stipitis NBRC1687 (standard stock) was used as strain.

A pre-culture condition was that 10 mL YPD (1% yeast extract, 2%peptone, 2% glucose) was used as a medium, and shaking culture wasperformed at 30° C. at 120 rpm.

The fermented liquid which had been passed through a filter (0.45 μm),and the fermented liquid which had not been passed through the filter(0.45 μm) were prepared, and the fermentation was performed.

An ethanol fermentation condition was that 100 mL of fermentation liquidwas used and shaking culture was performed at 30° C. at 120 rpm.

The fermentation conditions and the test results are shown in Table 2and Table 3.

TABLE 2 Nutrient, Final saccharide concentration Yeast Test Filter ex.*CSL* Glucose Xylose No. Solvent (0.45 nm) (%) (%) (%) (%) (2-1)Saccharide Absent 0 0 7.2 8.5 (2-2) solution Present (2-3) from Absent1.0 1.0 (2-4) biomass Present treated at high temperature (C5saccharide) Condition: 100 mL of fermented liquid, 30° C., 120 rpmShaking culture *Yeast ex.: Yeast extract *CSL: Corn steep liquor Strainused: Pichia stipitis NBRC1687 (standard strain) Pre-culture conditions:Medium 10 mL YPD (1% Yeast ex.*, 2% Peptone, 2% Glucose) Conditions 30°C., 120 rpm Shaking culture

TABLE 3 Final concentration of Glucose, Xylose, or EtOH ConcentrationFermentation Glucose efficiency Test No. (%) Xylose (%) EtOH (%) (%)(2-1) 5.9 7.2 N.D. 0 (2-2) 3.7 7.1 0.9 11 (2-3) 5.4 7.4 N.D. 0 (2-4)N.D. 5.0 3.0 38 N.D.: Not Detected

FIG. 5 and FIG. 6 are charts illustrating the results of decreasedamounts of carbon dioxide in the ethanol fermentation test, in which thehorizontal axis shows time, and the vertical axis shows a CO₂ decreasedamount.

As illustrated in FIG. 5 and FIG. 6, the fermentation test showed thatthe difference in the decreased amount of carbon dioxide appeared afterabout 90 hours passed in Test 2-2 (no nutrient, presence of the filter)compared to Test 2-1 (no nutrient, no filter).

The difference in the decreased amount of carbon dioxide appeared afterabout 20 hours passed and after that the decreased amount was remarkablyincreased in Test 2-4 (presence of nutrient, presence of the filter)compared to Test 2-3 (presence of nutrient, no filter).

The fermentation efficiency was 11% in Test 2-2, and the fermentationefficiency was 38% in Test 2-4.

It was confirmed, therefore, that when the treatment with a filter (0.45μm) was performed, the water-slightly soluble fermentation inhibitorysubstances are removed, resulting in performance of good fermentation.

As described above, it was proved that when the water-slightly solublefermentation inhibitory substances were removed by the saccharidesolution purification means, the saccharide solution including lessimpurities could be obtained, and the fermentation inhibition could beremarkably suppressed in the alcohol fermentation treatment in thesubsequent steps.

REFERENCE SIGNS LIST

-   -   50 hydrothermal decomposition apparatus    -   51 biomass feedstock    -   52 biomass supplying unit    -   53 apparatus body    -   54 conveying screw means    -   55 pressurized hot water    -   56 biomass solid component    -   57 biomass discharging unit    -   90 cooling means    -   101A biomass treated liquid at a high temperature (pressurized        hot water effluent)    -   101B cooled treated liquid    -   102 enzyme    -   103 enzymatic saccharification tank    -   104 saccharide solution    -   110 saccharide solution purification means    -   141: fermentation tank    -   142 yeast    -   200A to 200C alcohol fermentation apparatus that uses biomass as        a feedstock

The invention claimed is:
 1. A fermentation apparatus that uses biomassas a feedstock comprising: a hydrothermal decomposition apparatus thatbrings a biomass feedstock including at least cellulose, hemicellulose,and lignin into countercurrent contact with pressurized hot water andperforms a high temperature and high pressure treatment in a temperaturerange of 180° C. to 240° C. so as to produce a biomass treated liquidcontaining a pressurized hot water soluble component of the biomassfeedstock; a cooling means that is provided downstream of thehydrothermal decomposition apparatus and cools the biomass treatedliquid which has been discharged from the hydrothermal decompositionapparatus; a saccharide solution purification tank that is provideddownstream of the cooling means and saccharifies the cooled treatedliquid with an enzyme so as to obtain a saccharide solution; a firstcirculation line that connects between a bottom portion of thesaccharide solution purification tank and an upper portion of thesaccharide solution purification tank to circulate the saccharidesolution; a second circulation line that connects between the bottomportion of the saccharide solution purification tank and the upperportion of the saccharide solution purification tank to circulate thesaccharide solution; a solid-liquid separation apparatus that isinterposed in the first circulation line and removes a fermentationinhibitory substance contained in the saccharide solution, thefermentation inhibitory substance being a substance that is contained inthe pressurized hot water soluble component, and that is in a liquidstate in the temperature range of 180° C. to 240° C. and becomessolidified or colloidal at a temperature of 60° C. or lower; a foreignsubstance removing unit that is interposed in the second circulationline and further provided with a microfiltration (MF) membrane by whichthe fermentation inhibitory substance is further removed; a dilutiontank that is disposed downstream of the foreign substance removing unitand adds water thereto so as to dilute the saccharide solution fromwhich the fermentation inhibitory substance has been removed; a waterseparation unit that is provided with a reverse osmosis (RO) membraneand removes water from the diluted saccharide solution so as to obtainconcentrated saccharide solution; a fermentation tank that ferments theconcentrated saccharide solution; and a first measurement unit thatmeasures either or both of a turbidity or/and a light absorbance of thesaccharide solution from which the fermentation inhibitory substance hasbeen removed.
 2. The apparatus according to claim 1, further comprisinga second measurement unit that measures either or both of a turbidityand a light absorbance of the saccharide solution after addition ofyeast.